1. Field of the Invention
The present invention relates to a direct current linear motor commonly used for moving an object to be moved with high accuracy in, for example, a motion mechanism such as a machine tool or industrial robot, and a drive unit wherein a guiding device for guiding an object is added to said direct current linear motor.
2. Description of the Prior Art
An example of this type of direct current linear motor and drive unit of the prior art is shown in FIG. 1.
As shown in the drawing, this drive unit has a long base member 1 acting as a track rail, and a slider in the form of moving body 2 which moves along said base member 1. More specifically, a plurality of rollers (not shown) are provided in moving body 2, and these rollers roll over a track (not shown) formed along the lengthwise direction in base member 1.
Overhang 1a is formed on one side of base member 1, and a detected element in the form of linear scale 4 is provided on said overhang 1a roughly over its entire length. In contrast, small bracket 2a is provided on the side of moving body 2, and detection elements in the form of light emitting element 5a and light receiving element 5b are mounted on said small bracket 2a. A position detection device for detecting the position of moving body 2 with respect to a track rail in the form of base member 1 is composed by linear scale 4, light emitting element 5a and light receiving element 5b.
On the other hand, a direct current linear motor, which composes a drive unit together with the above-mentioned guide unit, is composed in the manner described below.
As shown in the drawing, said direct current linear motor is composed of a primary side equipped with a large number of armature coils 7, arranged on base member 1 in the lengthwise direction of said base member 1, and a secondary side having a field magnet (not shown) attached to the bottom surface of moving body 2 to oppose each of said armature coils 7. Each armature coil 7 is wound into the shape of a rectangular loop, attached to coil substrate 8, and fastened together with said coil substrate 8 to base member 1 by screws 9. In addition, the above-mentioned field magnet is magnetized by alternately arranging a plurality of N and S magnetic poles along the direction in which moving body 2 is to move, namely the lengthwise direction of base member 1.
In the drive unit having the constitution described above, by supplying a prescribed current to armature coils 7, thrust is produced based on Fleming's right hand rule between the primary and secondary sides. For example, if base member 1 to which the primary side is coupled, is taken to be the stationary side, moving body 2 integrated into a single unit with the secondary side is moved by this thrust. The position of moving body 2 with respect to base member 1 is then detected by the position detection device previously described.
Next, the following provides an explanation of a second example of a drive unit of the prior art based on FIG. 2. Furthermore, since this drive unit is composed in the same manner as the first example of a drive unit of the prior art shown in FIG. 1 with the exception of the following points, an explanation of the entire unit will be omitted, with the explanation only focusing on the essential portions.
As shown in the drawing, in said drive unit, each armature coil 7 is supported by a separate coil substrate 10, and the primary side is formed by linking these together.
In the case of fabricating various lengths of direct current linear motors and drive units in the constitution shown in the form of the first example of the prior art described above, since a long coil substrate 10 must be fabricated to match their entire lengths, a large mold and so forth is required for each type manufactured resulting in the disadvantage of high costs. In addition, in the case of attempting to incorporate said direct current linear motor and drive unit in an apparatus such as a machine tool, unless a direct current linear motor and drive unit is available that matches the operating stroke required by said apparatus, that having a stroke larger than said operating stroke must be selected, thus resulting in the disadvantage of not only excess costs, but also increased size of the apparatus.
On the other hand, in the constitution shown in FIG. 2 as a second example of the prior art, since coil substrate 10 is provided separately to correspond to each armature coil 7, at the time of assembly, assembly work is required involving coupling each armature coil 7 to each coil substrate 10, and then sequentially mounting these coupled assemblies in a row on base member 1. In said constitution, a direct current linear motor and drive unit of a desired stroke can be obtained by increasing or decreasing the number of individual coil substrates mentioned above linked together. However, since a large number of parts must be fabricated and manipulated in this manner, this constitution has the disadvantage of requiring numerous man-hours and having difficulty in reducing costs.
Continuing, the following provides an explanation of a drive unit containing a direct current linear motor as a third example of the prior art based on FIGS. 3 through 5. Furthermore, since this drive unit has a constitution similar to each of the drive units shown in FIGS. 1 and 2, with the exception of the following points, an explanation of the entire unit will be omitted, with the explanation only focusing on the essential portions.
As is clear from FIGS. 3 and 4, in said drive unit, each armature coil 7 and coil substrate 8 is fastened together to base member 1 to the outside of said coil substrate 8 by fastening members in the form of countersunk head screws 9 of which two each, for example, are inserted for each of said armature coils 7. Spacers 12 are inserted onto each of said countersunk head screws 9. These spacers 12 are for preventing warping and so forth of coil substrate 8 caused by fastening of countersunk head screws 9, and are formed into a circular shape as is clear from FIG. 5.
In a direct current linear motor containing the drive unit having the above-mentioned constitution, spacers 12 for preventing deformation of coil substrate 8 caused by tightening force during fastening of said coil substrate 8 are fit onto the end of each countersunk head screw 9. In said constitution, since a large number of parts including said spacers 12 have to be fabricated and manipulated, a large number of man-hours are required thus presenting a problem to be solved in terms of attempting to reduce production costs.